Enroute climb

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Joe hart

Filing Flight Plan
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Joehart96
Why enroute climb on a Cessna 172 sp is considered as 85kt Instead of 74kt (initial climb)
 
Probably an efficient climb speed considering forward progress and fuel burn.

Initial climb is more concerned about obstacles and such.
 
Also, you are pitched less. Likely 3* versus 6-8*.
 
En route climb is a compromise. You are no longer concerned with getting away from the ground and terrain as quickly as possible, would like to go faster but still have a decent climb rate. The gotcha issues become more about seeing traffic and engine cooling. The lower pitch of about 10 KTS faster than Vy helps with all those goals.

Parenthetically, I was curious enough about this once to look at the POH for a few different make/models. Seems that ~10 KT spread is pretty common for piston singles.
 
midlifeflyer said:
Parenthetically, I was curious enough about this once to look at the POH for a few different make/models. Seems that ~10 KT spread is pretty common for piston singles.
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I suppose for most. Vy on my 201 is 88kts, but once at 2500agl or so I transition to cruise climb of about 120kts. I can still maintain 500fpm at that speed to ~5000agl and then 300fpm to 9-10000msl. Good compromise of speed vs climb. Since the 201 has such a high redline I also like to cruise descend, usually 180-185kts on the downhill side if the air is relatively smooth.
 
Why do you not drive in first gear all the way to your destination?
 
Cruise climb serves two purposes. First, engine cooling is better. Second, visibility over the nose is also better.

Having said that, there are times when you have to climb at Vy. Like high altitude climbs. Otherwise you don't climb at all.
 
Bill Jennings said:
I suppose for most. Vy on my 201 is 88kts, but once at 2500agl or so I transition to cruise climb of about 120kts. I can still maintain 500fpm at that speed to ~5000agl and then 300fpm to 9-10000msl. Good compromise of speed vs climb. Since the 201 has such a high redline I also like to cruise descend, usually 180-185kts on the downhill side if the air is relatively smooth.
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show-off.
 
Bill Jennings said:
I suppose for most. Vy on my 201 is 88kts, but once at 2500agl or so I transition to cruise climb of about 120kts. I can still maintain 500fpm at that speed to ~5000agl and then 300fpm to 9-10000msl. Good compromise of speed vs climb. Since the 201 has such a high redline I also like to cruise descend, usually 180-185kts on the downhill side if the air is relatively smooth.
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I usually do the same as you. Even at higher speeds when just changing altitudes at cruise. No reason not to.

But notice that in the post you quoted from I said
midlifeflyer said:
I was curious enough about this once to look at the POH for a few different make/models.
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The Mooney 201 POH recommends 90-100. There's your ~10 KT spread.
 
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midlifeflyer said:
But notice that in the post you quoted from I said

The Mooney 201 POH recommends 90-100. There's your ~10 KT spread.
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Yeah, true, haven't looked at it in a while, but like you faster seems to be better. I can live with 500fpm at 120kts as a nice compromise.
 
Cruise climb can be different from initial climb. Initial climb might be to get over obstacles and whatnot, but the more restricted airflow can increase engine temperatures. In my aircraft the initial climb is slower just so I can get the gear and flaps stashed. I then head into cruise climb.
 
There is also something to be said for actually being able to SEE over the nose during a climb. The benefits of extra cooling, more forward speed and everything else people have said also apply. If you are at Vy or Vx even, you aren't going to get much visibility over the nose in some airplanes at that speed/angle.

I really don't see the point in maintaining Vy all the way up to target altitude. The Piper I owned recommended a 100 MPH climb speed to allow for visibility over the nose and "passenger comfort". Why would I disregard that and climb at 85 mph or Vy? Also (for Piper's anyway) the #3 cylinder sometimes is a bit of a hot spot. You want a lot of air on that during climbout to cruise altitude.

All that vertical speed you're getting is translating into less forward speed, less cooling, more fuel, etc. Doesn't seem beneficial unless there's some sort of obstacle or ODP you need to follow to get out safely.
 
Cruise climb is much more efficient. Also helps keep those CHTs in check.
 
Doggtyred said:
Better engine cooling. Covering more lateral distance. Lower the nose and see better.
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This site is so great. I was studying the POH and club checklist for takeoff, and climb en route and was going to ask my CFI about it but now I got the answer.
 
With a good engine monitor that shows CHT's you'll quickly learn the reason for VY / VX during the climb!
 
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